Surface condenser, the condenser broadly applied in power plant cooling has been known for more than a century. Steam turbines fitted with surface condenser may be cooled either by wet, i.e. evaporative cooling systems, or by a dry cooling system. The central element of the approach described in FR 877 696 covering Prof. László Heller's invention is the so-called direct contact condenser (i.e. mixing condenser) which can be applied instead of the usual surface condenser in power plant cycles. The direct contact condenser makes dry (air) cooling more efficient. The system so implemented is generally called a Heller-system.
In the technical field, the joint application of surface and direct contact condensers in combined dry/wet cooling systems has emerged repeatedly. Most of the related publications do not offer actual design solutions for the hybrid condenser. One of the first patent documents relating to combined dry/wet cooling systems, U.S. Pat. No. 3,635,042 additionally describes a condenser in the schematic diagram of the cooling system, where the injection of dry system cooling water is shown in the surface condenser body. A similar schematic diagram is depicted in U.S. Pat. No. 3,831,667. In this case, according to FIG. 1, the cooled water coming from the dry cooling circuit is injected at a higher location with respect to the tubes of the cooling surface associated with the wet cooling circuit. The known arrangement of having one unit above the other is not advantageous, because about fifty times as much water as the quantity of condensate generated outside the tubes of the surface condenser is poured onto the tubes. Therefore, the path of steam flow between the tubes is mostly blocked and the cooling effect of the surface condenser tubes is deteriorated, because due to the condensing of one part of the steam, the already heated up water coming from the dry cooling circuit functions as an insulating layer between the wall of the tubes cooled from inside and the not yet condensed steam.
A hybrid condenser associated with a so-called plume abating wet/dry tower is described, and a related schematic construction diagram is also presented in U.S. Pat. No. 6,233,941 B1. In FIG. 2 of the document, the two condenser parts are arranged in separate housings, which not only entails extra costs, but also results in an extra pressure drop, i.e. in the deterioration of efficiency, because of the branching of the expanded steam. FIG. 1 of the document shows a solution, where the surface and direct contact condenser parts are located within one housing. One part of the exhaust steam from the turbine condenses on the surface condenser; this part of the steam flow is subjected to cooling first. The steam which is not condensed here and the steam which bypasses the surface condenser are condensed in the space assigned to the direct contact condenser. Arranging the condenser parts side by side significantly enlarges the required condenser cross section, which results in a cost increase. The known arrangement may only be used at the most in the combined wet and dry mode of operation, and hence the purely dry operation desirable in cold weather, when the functioning of the direct contact condenser part is required only, is therefore inefficient. The surface condenser part comprises the conventionally applied elements, and the direct contact condenser part reflects the design of Heller's direct contact condenser. According to the prior art solution, a steam baffle plate is arranged between the surface condenser part and the direct contact condenser part, and the plate is designed to turn the steam path partly into a counter-flow with the water introduced into the direct contact condenser. It is to be noted that because the baffle plate is arranged in the path of the steam flow directed to the direct contact condenser, the application of this baffle plate results in a substantial steam pressure drop. It is also a disadvantage that the steam is introduced into the direct contact condenser part as a vortex after repeated changes of direction, which again deteriorates the efficiency of the condenser part.
A dry/wet cooling system is described in WO 2011/067619 A2, which is aimed at significant annual water saving in comparison with the purely wet cooling system. According to the document, the two separated dry and wet cooling circuits may be integrated partly through water-water heat exchangers, and partly through a hybrid condenser. The large annual water saving (70 to 90% with respect to the purely wet cooling system) necessitates the running of the cooling system in both purely dry and varying wet assisted modes. One of the most important components of the system is a hybrid condenser, which comprises in a single condenser body the direct contact condenser which utilises the cooling effect of the dry cooling circuit, and the surface condenser which uses the cooling effect of the wet cooling circuit. The document does not provide information about the preferred structure and design of a hybrid condenser.
A number of documents introduce separate direct contact or surface condenser solutions, as well as their auxiliary equipment. DE 1 014 568 discloses equipment for dumping turbine bypass steam into a surface condenser. U.S. Pat. No. 3,520,521 discloses sectionalized heavy duty condensers. Both EP 0 467 878 A1 and DE 1 451 133 disclose direct contact condensers.
To implement the condensation of exhaust steam from the turbine, the available space is limited both horizontally and in depth, especially in the case of a steam flow leaving the turbine downwards, which is the most common approach. In lateral directions, the support columns of the turbine table and in depth the machine hall baseplate and the NPSH (net positive sucktion head) requirement of condensate extracting pumps represent restrictions. This necessitates that the hybrid condenser shall be a compact equipment, and it is also desirable to avoid any potential negative reaction of the two condenser parts on each other. Prior art approaches failed to resolve these issues.